1. Field of the Invention
The invention concerns an optical device, notably for a motor vehicle, such as a lighting and/or signaling device having in particular a photometric function useful for circulation of the vehicle on roads, enabling the vehicle to be seen by other vehicles or the driver of the vehicle to see outside.
2. Description of the Related Art
It is known, in particular from the document DE 10 2007 018 985, which document is incorporated herein by reference and made a part hereof, to use surface-emitting light sources, in particular an organic light-emitting diode, as the light source of a motor vehicle signaling device. An organic light-emitting diode-type light source of this kind enables provision of homogeneous light.
The brightness of an organic light-emitting diode of the present-day technology may not be sufficient to provide some signaling functions (such as “side light”, “brake light” and “high-level brake light” signaling functions). An organic light-emitting diode of the present-day technology typically provides a brightness of 1000 Cd/m2 whereas a brightness of 5000 to 10 000 Cd/m2 would be required for the aforementioned functions.
There is known from the document DE 10 2007 018 986, which document is incorporated herein by reference and made a part hereof, a motor vehicle passenger compartment lighting device comprising a set of organic light-emitting diodes to which optical elements are stuck.
Vehicle signaling device are known from the documents DE 202 07 799 and EP 1 485 959, which are equivalent to U.S. Patent Publication 2005/0117347, which documents are incorporated herein by reference and made a part hereof.
To summarize, organic light-emitting diodes can have the following features:                homogeneous light emission,        substantially plane light-emitting surface,        relatively low brightness.        
Although the first characteristic is favorable (because homogeneous light is appreciated by motor vehicle manufacturers, for example), the other two characteristics may be problematic in that a light is often curved. Moreover, the statutory minimum luminous intensity values (4 Cd for a headlamp) would impose large light-emitting areas.